This book constitutes the refereed proceedings of the International RuleML Symposium on Rule Interchange and Applications, RuleML 2009, held in Las Vegas, Nevada, USA, in November 2009 - collocated with the 12th International Business Rules Forum.

The 12 revised full papers and 17 revised short papers presented together with the abstracts of 3 keynote lectures were carefully reviewed and selected from 56 submissions. The accepted papers address a wide range of rule topics, including traditional topics, such as complex event processing using rules (a RuleML stronghold with several past invited speakers form the area and many past papers on this topic), to rules for transformations and rule extraction, applications of rule systems to handle data and processes, investigations on how to deploy rules on the Web to use of rules to model uncertainty and norms.